Hi All!
I just wanted to take a minute since there is so much herbal discussion going on at present.  There are a few things to remember when using or recommending (or even questioning the use of) herbal therapies in breastfeeding.  Herbs are much like standardized FDA approved drugs.  Just as an FDA approved drug is designed to alter a current state of "health" (or lack of) within the body, herbs are God designed to do the same thing.  This means that several things must be remembered when using herbs.  First of all, just as you can overdose on a prescription medication, the same is true for herbs.  Too much of a good thing... etc.  But let's also try to remember that just because herbs don't have the FDA stamp of approval doesn't make them all bad or something to be avoided or constantly questioned. 
Black Cohosh, for example is an excellent herbal not only for its estrogenic effects but also as an anti-spasmodic and relaxant.  However, don't take too much of it...just like to much aspirin, or cold syrup, or pain medication.  Also, due to its estrogenic effects and effect on the uterus, it should be avoided in preganancy except as an aid to facilitate labor in the last 2 weeks of pregnancy.  Standard accepted dosage is 10 - 60 drops of tincture or 3 - 9 grams standard decoction.  Over 7 years in the study use and recommendation of herbs has never shown a problem in its use in breastfeeding.
Regarding goldenseal, it is contraindicated in pregnancy.  It can, however, be used for short periods in lactation.  The main concern with the use of goldenseal in lactation is its drying effect over a significant period of time.  As with all my clients, I never ever recommend the use of goldenseal taken "daily as a preventative" due to its drying and irritating effect on mucus membranes over a significant period of time.  
Should anyone have questions regarding the use of herbals during breastfeeding or not, I hope that you would not hesitate to contact me and ask...I'm happy to help however I can.
As I have been requested to alter my signature line for use on this discussion list, I'll just note that I do have a toll-free number available where I can be reached for answering quick herbal questions at no charge.  This is just a way that I try to make myself available for folks with questions.

Wishing you health and wellness!
Tami Karnes
Certified Herbalist

One With Nature
1-800-230-5166